Weight Groups

[Leo Lazauskas]

Colleagues:
I am having trouble finding a comprehensive set of "standard" weight groups.
At the moment, I have my program set up with the following categories...

WEIGHT GROUP
100 Structure
200 Propulsion
300 Electrical
400 Command
500 Auxiliary
600 Outfit
700 Armament
Cargo
Crew & Effects
Provisions
Fresh Water
Lube Oil

Users can estimate (or supply constants for certain equations) to estimate each category. Fuel is the remainder after all other items are summed, and its weight is used to estimate the (Breguet) range of the vessel at each speed.

Mr Ad Hoc suggested another category to account for the weight of oil sitting in engine sumps. Is there a specific group number for this and any other items I should include?

I tried googling for "Weight Groups" and got some unpleasant surprises when I hit "Images" by mistake.

Leo.

[MikeJohns]

Leo
you add lubricating oil and coolant in systems as a group if the machinery was taken at 'dry' weight.

other omissions and usual groups

Weight of Paint
Water services domestic and sanitary. (hardware )
Insulation
Deck gear (incl windlass chain anchors, davits cranes etc)
The Galley equipment on a large vessel can be significant
Air conditioning, heating, fans, ducting

[Leo Lazauskas]

Originally Posted by MikeJohns

Leo
you add lubricating oil and coolant in systems as a group if the machinery was taken at 'dry' weight.

Thanks, Mike.
Is that sometimes designated as 800 Systems or doesn't it have a "standard" code number?

Leo.

[Ad Hoc]

Originally Posted by Leo Lazauskas

Is that sometimes designated as 800 Systems or doesn't it have a "standard" code number?

Leo.

Correct 800 is "Fluids in Systems", such as entrained water in waterjets, or fuilds in pipes, or oil in engines etc etc.

[MikeJohns]

Leo
I'm not in my office, I'm not sure but I think it might be worth looking at a paper: RINA "Preliminary warship design" 1993

Good to see you John !

[Leo Lazauskas]

Originally Posted by Ad Hoc

Correct 800 is "Fluids in Systems", such as entrained water in waterjets, or fuilds in pipes, or oil in engines etc etc.

Thanks. Are there any standard groups? E.g. is there a 900 Something?

And, Hah! You show the same resolve in giving up posting as I do in giving up smoking

Leo.

[Ad Hoc]

Leo

The old NES i was brought up on has now changed. It was harmonised into Minsitry of Defence Standards.

Group 800, which in my day was generally Fluids in Systems, has been expanded to be Variable Load:

“..This Group includes all items of variable load, defined as those shipboard items which are consumable or subject to frequent change, e.g. crew and effects, ammunition, aircraft, military vehicles, unmanned vehicles, stores, provisions, spare parts, liquids and gases including gases in bottles…”

A consumable is strictly speaking part of the deadweight...ie like fuel or water, and should not be confused with fluids in pipes or engines etc which are required for the system to work and hence not "consumed".

see attached.

Can’t send attachments via PM…hence the ‘posting’

[daiquiri]

Hi Leo,
I have googled for ESWBS weight groups and have found the xls sheet (many thanks to Thai Navy ) which I am attaching here. It contains 4 and 5-digit codes for various components and can be personalized to suit your needs. You can find many reference texts in interent which use this numbering system, the google search term should include the word "ESWBS".
Cheers!

P.S.
It is interesting to note the big difference between UK MoD system posted by Ad Hoc and the U.S. ESWBS. Considering that we are living in a world where even fruit and vegetables' sizes are being standardized, and also the fact that Both US and UK are part of the NATO, one would expect to see more or less the same numbering system, with perhaps some minor variations.

[Leo Lazauskas]

Thanks all!
I might stick to the list I posted for the time being. It looks like it should be sufficient at the very early design stage. Using "Group 800: Variable Loads" instead of "Cargo" isn't worth worrying about.

If we want a real argument and a few laughs, wait until you see my Equipment Numeral Method for estimating the structural weight of aluminium catamarans!

Leo.

[BMcF]

err...you did say that its the structural weight only that will pop out of your new design tool? Interesting.

You will be updating it for composite hulls next, I presume?

[Leo Lazauskas]

Originally Posted by BMcF

err...you did say that its the structural weight only that will pop out of your new design tool? Interesting.

You will be updating it for composite hulls next, I presume?

Of course it can handle plastic boats, Bruce!

The user can choose to enter actual weights in tonnes for the structure, or the weight fraction of the total, or they can supply their own values for coefficients in certain formulas I provide.

For the structural weight group, I have included in the demo version one such formula due to Karyannis and Molland for aluminium monohulls and cats with lengths from 50m to about 125m.

I also have a three parameter formula due to Watson and Gilfillan for steel monohulls. (The formula of Karyannis and Molland is just a modification of Watson's and Gilfillan's, as any fule know.)

These formulas can be used for plastic boats if the user knows the appropriate values of the constants for the hull structure, the super structure, and the cross-structure for multihulls, ACV and SES.

I have attached an old report for a SES with the same dimensions as the Giam catamaran example. Running the demo should produce similar results for the off-cushion case (i.e. in "pure" catamaran mode). Results will not be identical because I have completely re-written the near-field and squat calculations since then, and I have improved some of the drag calculations. The demo doesn't include effects of squat, but you can include it by modifying the "squat.flo" file.

Running the "giam_drag.bat" file in the Flotilla 2.07 demo I posted in the Software Forum should produce the output shown at the end of this post.

In the "estweight.flo" input file, you can change the way the program estimates structural weight by modifying the entries with a plain text editor. The first few lines in the demo input file for the "Giam" catamaran are (with hashes signifying comments):

##################################################
# estweight.flo
# Set up as a military vessel with very approximate weight fractions.
##################################################
estweight input_type
0
# estweight input_subtype
0
# Structure: input_type
0
# Structure: input_subtype
1
# Structure: Constants
0.43

Input type 0 and sub-type 1 for Structure forces the program to use weight fractions. The structural weight fraction is specified here as 0.43, i.e. the actual structural weight is 114.69 tonnes.

Karyannis' and Molland's equipment numeral for catamarans, requires 7 constants. (See the attached report).

To use the equipment numeral method, change the values in the "estweight.flo" file to read:

# estweight input_type
0
# estweight input_subtype
0
# Structure: input_type
1
# Structure: input_subtype
0
# Structure: Constants
3025.0
0.85
1.6
0.00064
1.7
0.39
0.9

Using a value of 1 for the Structure input type, and 0 for the subtype, forces the program to use the Karyannis-Molland formula.

Running the example now should give a structural weight of 104.99 tonnes. (Note that the length of the catamaran in this example is shorter than the range of lengths used by Karyannis and Molland to derive their formula, so I'm not claiming that the estimate is reasonable.)

The estimated (Breguet) range of the vessel is greater than for the original example using a weight fraction because the estimated structural weight is lower. The weight saved on structure is available as fuel, hence the greater range.

A very serious deficiency of the program in its present form is that there is no allowance for margins. I'm choosing to leave that as an "exercise" at this stage.

All the best,
Leo.

Here's the output I get when running the demo "giam_drag.bat" file. I deleted some entries for brevity.

Sorry, I don't know how to retain spacing in posts to boatdesign.net so it looks like a madwoman's lunchbox.

FLOTILLA: CATAMARAN DRAG
======================= COMPONENT CENTRES ========================
Xcentre (m) Ycentre (m)
Hull 1 0.00000E+00 -0.51250E+01
Hull 2 0.00000E+00 0.51250E+01
Superstructure 0.00000E+00 0.00000E+00
Deckhouse 0.90000E+01 0.00000E+00
====================== PRINCIPAL DIMENSIONS ======================
V (m^3) L (m) B (m) H (m)
Hulls 0.65000E+03 0.40000E+02 0.32500E+01 0.45000E+01
Superstructure 0.38880E+04 0.48000E+02 0.13500E+02 0.60000E+01
Deckhouse 0.43200E+03 0.16000E+02 0.67500E+01 0.40000E+01
OVERALL 0.49700E+04 0.48000E+02 0.13500E+02 0.14500E+02
====================== UNDERWATER GEOMETRY =======================
V (m^3) L (m) B (m) T (m)
Hull 0.12999E+03 0.40000E+02 0.32500E+01 0.22500E+01
DISPLACEMENT 0.12999E+03
========================== SQUAT & DRAG ==========================
U(m/s) dZb(m) dZs(m) Rt(N)
0.51444E+01 0.00000E+00 0.00000E+00 0.14396E+05
...
0.15433E+02 0.00000E+00 0.00000E+00 0.18484E+06
============================ WEIGHTS =============================
WEIGHT GROUP METRIC TONS FRACTION
100 Structure 0.11469E+03 0.43000E+00
200 Propulsion 0.37340E+02 0.14000E+00
300 Electrical 0.80013E+01 0.30000E-01
400 Command 0.80013E+01 0.30000E-01
500 Auxiliary 0.80013E+01 0.30000E-01
600 Outfit 0.16003E+02 0.60000E-01
700 Armament 0.40007E+02 0.15000E+00
LIGHTSHIP 0.23204E+03 0.87000E+00
Cargo 0.00000E+00 0.00000E+00
Crew & Effects 0.26671E+01 0.10000E-01
Provisions 0.66678E+00 0.25000E-02
Fresh Water 0.11202E+02 0.42000E-01
Lube Oil 0.26671E+01 0.10000E-01
Fuel 0.17470E+02 0.65500E-01
DEADWEIGHT 0.34672E+02 0.13000E+00
GRAND TOTAL 0.26671E+03 0.10000E+01
============================ PROPULSION & RANGE ============================
U(m/s) Weight/Rt SFC(g/kW.h) OPC Ps(W) Range(km)
0.51444E+01 0.18168E+03 0.52875E+04 0.43000E+00 0.17223E+06 0.36743E+03
...
0.15433E+02 0.14150E+02 0.36262E+03 0.67000E+00 0.42578E+07 0.65018E+03

[conceptia]

thanks for the NES document. I still lack a lot of NES documents I suppose...

[BMcF]

Leo;

uh...it's 'Bill'..not Bruce.

Well hasn't this turned interesting. I downloaded your attachment and will take the time to go through it for sure. I know a 'little bit' about the Skjold...and just happen to be staring out my office window at several of the Skjold-class series vessels as I am typing this.


I will enjoy playing around with your results as they compare to the vessel. I'm always on the lookout for 'another cool free tool from Leo' anyway...

[Leo Lazauskas]

Originally Posted by BMcF

Leo;

uh...it's 'Bill'..not Bruce.

Well hasn't this turned interesting. I downloaded your attachment and will take the time to go through it for sure. I know a 'little bit' about the Skjold...and just happen to be staring out my office window at several of the Skjold-class series vessels as I am typing this.

Sorry, Bill, I know a Bruce McF who is a naval architect and you guys all look the same on the net.

The vessel I use is very much a mock-up of the Skjold. I had to guess many of the dimensions which isn't all that important.

As you can see, I tend to lurk around the outer arms of the design spiral, or levels of Hell, or whatever you call it. (Naval arch's are deeper down, and I assume accountants and male lawyers are at the very centre of the deepest level.)

The intention of the tool is to allow users a reasonably fast method to assemble the major components and to roughly estimate power requirements and the range of the putative vessel. As you can see from the awesome graphics in the report, it's up to the designer to sculpt the blocks into something more realistic.

Havagoodweekend!
Leo.

[BMcF]

The graphics were truly awesome indeed.